The stats are revealing.
If you're not doing Criminal Background Checks for every coach and volunteer at a youth rugby camp, you're just asking for trouble. Many liability insurance policies are "silent" on the issue of abuse/molestation, or flatly exclude the coverage. Those policies that include Abuse/Molestation, definitely require Criminal Background Checks for all adults associated with the youth camp or league.
If someone balks at paying for their own criminal background check, simply ask them to not attend the camp. Sorry, but that's the way it is.